The present invention relates generally to power systems and, more particularly, to power systems including internal combustion engines with power turbines.
During operation of a mechanical turbo compound system on an internal combustion engine there are times when the power flow reverses. That is, power from the engine is actually transferred to the shaft of the turbo compound power turbine. During normal operation of the system, energy from the exhaust is used to drive the power turbine. The standard flow of energy is from the output shaft of the power turbine to the engine crankshaft. The power reversal occurs during lower engine speed and load conditions when the exhaust flow becomes too low to drive the turbo compound turbine at a power level above what is necessary to drive, power to the crankshaft. During these times of energy reversal, the power is actually moving from the engine to the power turbine of the turbo compound unit. The power reversal causes increased back pressure in the turbocharger turbine outlet thereby causing higher engine fuel consumption.
According to an aspect of the present invention, a power system comprises an engine comprising an exhaust line, a turbine in the exhaust line, a bypass line connected to the exhaust line upstream of the turbine and comprising a controllable bypass valve, and a controller arranged to control opening of the bypass valve, to bypass the turbine when at least one of an engine load, an engine speed, and an exhaust line pressure are below predetermined levels.
According to another aspect of the present invention, a power system comprises an engine comprising an exhaust line, a turbine in the exhaust line, a turbine shaft of the turbine being coupled to a crankshaft of the engine to permit transmission of power between the turbine shaft and the crankshaft, a bypass line connected to the exhaust line upstream of the turbine and comprising a controllable bypass valve, and a controller arranged to control opening of the bypass valve to bypass the turbine when the engine is operated such that power is transmitted from the crankshaft to the turbine shaft.
According to yet another aspect of the present invention, a method of operating a power system comprises exhausting as from an engine into an exhaust line, and controlling a bypass valve to open a bypass line arranged to bypass a turbine in the exhaust line when the engine is operated such that power would otherwise be transmitted from the crankshaft to the turbine shaft.